On 08/22/2013 07:17 PM, Richard Zhao wrote: > On Fri, Aug 23, 2013 at 04:36:53AM +0800, Stephen Warren wrote: >> On 08/22/2013 12:43 AM, Richard Zhao wrote: >>> DMA client device driver usually needs to know at probe time whether >>> dma controller has been registered to deffer probe. So add a help >>> function of_dma_check_controller. >>> >>> DMA request channel functions can also used to check it, but they >>> are usually called at open() time. >> >> This new function is almost identical to the existing >> of_dma_request_slave_channel(). Surely the code should be shared? > > ofdma->of_dma_xlate(&dma_spec, ofdma); > The above is called holding of_dma_lock. If I want to abstract the > common lines, there' two options. What is the problem with acquiring the lock? If request_slave_channel() needs to take the lock, then there must be a reason which presumably applies to the other path too. ... >> But that said, I don't see any need for a new function; why can't >> drivers simply call of_dma_request_slave_channel() at probe time; > > It'll mislead user. channel supposed to be request at open time. I don't agree. >> from >> what I can see, that function doesn't actually request the channel, but >> rather simply looks it up, just like this one. The only difference is >> that of_dma_xlate() is also called, but that's just doing some data >> transformation, not actually recording channel ownership. > > xlate function request the channel if things go well. Oh. xlate should not do that; that's a design flaw. xlate should do nothing more than translate the DT content to an internal channel ID. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
